With the purpose of causing vehicles such as automobiles to properly operate, arousal level estimation devices for estimating an arousal level of a driver who is driving a vehicle have been conventionally developed.
The applicant of the present invention has proposed the technology that estimates a driver's arousal level by using the concept of a driver model in which driver's consciousness, determination, and operation are modeled (see, Patent document 1).
According to the arousal level estimation technology of Patent document 1, a driver model creation unit creates a driver model expressing a relationship between a virtual driver's input and a virtual driver's output by using a difference between a target azimuth angle and an actual azimuth angle (an azimuth deviation) as the virtual driver's input and an actual steering angle as the virtual driver's output. Then, a driver model operation amount acquisition unit acquires a driver model steering angle by inputting a current azimuth deviation into the driver model. An arousal level estimation unit estimates an arousal level of the driver based on a difference between the actual steering angle and the driver model steering angle.
The difference between the actual steering angle and the driver model steering angle is an effective index to evaluate whether or not an operation based on driver's determination (an actual steering angle) is based on a linear model (a driver model steering angle). Also, it has been known that when the operation based on the driver's determination (the actual steering angle) differs from the driver model steering angle, it is highly probable that the driver's arousal level is decreased. Accordingly, the arousal level estimation technology of Patent document 1 can estimate the driver's arousal level based on the difference between the actual steering angle and the driver model steering angle.